The program represents the decision of multiple investigators to bring their individual techniques, systems and ideas to bear on a common theme. The central focus is the regulation of secretion and synthesis of the three pituitary gonadotropic hormones (FSH, LH and PRL), the analysis of their actions on the gonads and the feedback regulation by hormonal signals on the hypothalamic/pituitary unit. Particular emphasis is placed on the study of FSH because of the relative lack of information about his hormone compared to the other gonadotropins. The levels of investigation range from the whole animal to the molecular. The strong collaborations among the laboratories and projects have resulted in many important findings and an excellent publications record. The present application for renewal includes five research projects and an administrative core: PROJECT I. Differential Regulation of Gonadotropins by Glucocorticoids [Schwartz PI; Linzer CoPI] PROJECT II. Regulation of and Role of FSH in Photoperiodic Response [Turek PI; Levine Co-PI] PROJECT III. Protein Phosphorylation in Granulosa Cells [Hunzicker-Dunn PI] PROJECT IV. Inhibin and Activin: Synthesis, Activities, and Receptors [Mayo PI] PROJECT V. Regulation and Function of Ovarian Prolactin Receptors [Linzer PI; Hunzicker-Dunn Co-PI] CORE A. Administrative Core [Schwartz PD] The exchange of methodologies and ideas among investigators made possible by a Program Project Grant have fostered a broader perspective on the complexities of the hypothalamic-pituitary-gonadal axis than would have been possible with individual research grants. Indeed it is the interactions fostered by this Program Project Grant that have resulted in substantial progress being made in the past five years in understanding the control and action of FSH and the differences and similarities between FSH and the other gonadotropins.